Build the Docker image without emulation

.github/workflows/release.yml

@@ -76,7 +76,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: docker/setup-qemu-action@v3
       - uses: docker/setup-buildx-action@v3
       - uses: docker/login-action@v3
         with:

Dockerfile

@@ -1,22 +1,27 @@
 # syntax=docker/dockerfile:1
 
+# Both build stages run on the build machine's own architecture (BUILDPLATFORM): the UI is the
+# same files everywhere and Go cross-compiles, so a multi-arch build never runs under emulation.
+
 # 1. Web UI (static files embedded into the binary)
-FROM oven/bun:1.4-alpine AS web
+FROM --platform=$BUILDPLATFORM oven/bun:1.4-alpine AS web
 WORKDIR /src/web
 COPY web/package.json web/bun.lock ./
 RUN bun install --frozen-lockfile
 COPY web/ ./
 RUN bun run build
 
-# 2. Server: pure Go, no cgo, so the result is one static file
-FROM golang:1.26-alpine AS server
+# 2. Server: pure Go, no cgo, so the result is one static file for the target platform
+FROM --platform=$BUILDPLATFORM golang:1.26-alpine AS server
+ARG TARGETOS
+ARG TARGETARCH
 WORKDIR /src
 COPY go.mod go.sum ./
 RUN go mod download
 COPY . .
 COPY --from=web /src/web/build ./web/build
 ARG VERSION=dev
-RUN CGO_ENABLED=0 go build -trimpath -ldflags "-s -w -X github.com/LowBloat/LowLex/internal/server.Version=${VERSION}" -o /out/lowlex ./cmd/lowlex \
+RUN CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH:-amd64} go build -trimpath -ldflags "-s -w -X github.com/LowBloat/LowLex/internal/server.Version=${VERSION}" -o /out/lowlex ./cmd/lowlex \
  && mkdir -p /out/data
 
 # 3. Runtime: CA certificates (for translation providers), time zones and a non-root user